The document summarizes key aspects of fetal skull development and its adaptation to the maternal pelvis during birth. It describes how the fetal skull is made of thin, compressible bones that are not fully formed at birth. It also outlines the major bones, sutures, fontanelles, and diameters of the fetal skull. Additionally, it discusses the structure of the maternal pelvis, including the false and true pelvis, inlet, cavity and outlet. Key diameters of the pelvis are defined that are important for fetal descent and birth. Finally, different types of female pelvises are described that can impact the birthing process.

1. Foetal Skull and
Maternal Pelvis
DR. SNEHA TIWARI,
B.A.M.S., M.S (AYU.)
ASSISTANT PROFESSOR AND CONSULTANT GYNAECOLOGIST,
DEPT. OF PRASUTI TANTRA & STRI ROGA,
G.J PATEL INSTITUTE OF AYURVEDA STUDIES AND RESEARCH,
ANAND,GUJARAT
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2. Introduction
 The foetal head is large in relation to the foetal body compared with
adult.
 The skull of the foetus is about one half the height at 2 months, more
than one fourth the height at four months, one fourth at birth, about an
eight at age 25
 Adaptation between the skull and the pelvis is necessary to allow the
head to pass through the pelvis during labour without complication.
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3.  The skull bones encases and protect the brain.
 Foetal skull is compressible, and made mainly of thin
liable tabular(flat) bones forming the vault.
 The foetal skull has three major parts:
• Vault of the cranium (Roof)
• Face
• Base
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4. Vault Bones 4

5. Sutures
 Flat bones of the vault are united together by the nonosssified membranes
attached to the margins of the bones. These are called sutures.
 THE SAGGITAL SUTURE: Lies b/w two parietal bones.
 THE CORONAL SUTURES : Run b/w parietal and frontal bones on either sides
 THE FRONTAL SUTURE : Lies b/w two frontal bones.
 THE LAMBDOIDAL SUTURES : Separate the occiput bone and two parietal
bones.
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6. Importance
 It permits gliding movement of one bone over the other
during moulding of the head.
 Digital palpations of sagittal suture during internal
examination in labour gives an idea of the manner of
engagement of the head, degree of internal rotation of
the head and degree of moulding of the head.
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7. Fontanelle
 Wide gap in the suture line is called FONTANELLE.
 ANTERIOR FONTANELLE: Formed by joining four sutures in midplane.
 Anteriorly frontal -. Posteriorly sagittal.
 On either side coronal suture.
 Diamond like shape.
 Ossified at 18months after birth.
Importance
 It facilitates moulding of the head.
 As it remains membranous long after birth, it helps in accommodating the marked brain growth,
the brain becoming almost double its size during first year of life.
 Palpation of the floor reflects intracranial status depressed in dehydration, elevated in raised
intracranial tension.
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 POSTERIOR FONTANELLE:
 Formed by junction of three sutures.
 Sagittal suture anteriorly. Lamboidal suture on either side
 Triangular in shape, Measure about 1.2 x1.2cm. its floor is
membranous but become bony at 3months.
 SAGGITAL FONTANELLE:-
 It is inconsistent in its presence.
 It is situated on the sagittal suture at the
junction of anterior to two-third and posterior
one-third.
 it has got no clinical importance.

9. Landmarks
 Occiput- is the occipital bone/external occipital protuberance.
 Sinciput- is the forehead region of foetal head.
 Parietal eminences- are the eminences of parietal on either side.
 Mentum- it is the chin.
 Vertical point- it is the centre of sagittal suture.
 Frontal point/ Nasion- is the root of nose.
 Sub occiput- is the junction foetal neck and occiput.
 Sub mentum- it is the junction between neck and chin.
 Glabella- the elevated area between the orbital ridge
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11. Diameter Of Skull
Anterior
Posterior/
Longitudinal
Transverse
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12. Transverse Diameter
 Bi parietal Diameter- Measure about 9.5cm. It extends between two
parietal eminences.
 Bi-temporal diameter- Measure about 8cm. It is the distance between
anterior-inferior ends of the coronal suture.
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13. Longitudinal Diameter
 Sub-occipitobregmatic- 9.5cm. The diameter from below the occipital protuberance to
the centre of the anterior fontanels.
 Sub-occipitofrontal- 10cm. The diameter from below the occipital protuberance to the
centre of the frontal suture.
 Occipitofrontal-11.5cm. The diameter from the occipital eminence to the glabella.
 Mentovertical-13.5cm. The diameter from the point of the chin to the highest point on the
vertex, slightly nearer to the posterior than to the anterior fontanelle.
 Submentovertical-11.5cm. the diameter from the point where the chin joins the neck to
the highest point on the vertex.
 Submentobregmatic-9.5cm. The diameter from the point where the chin joins the neck to
the centre of bregma
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15. Maternal Pelvis
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17. Pelvis
 Composed of four bones — two
innominate bones, sacrum and
coccyx.
 These are united together by four
joints — two sacroiliac joints,
sacro-coccygeal joint and the
symphysis pubis. The pelvis is
anatomically divided into a false
pelvis and a true pelvis
Pelvis
Bony
False True
Inlet Cavity Outlet
Soft
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18. Soft Pelvis
It’s formed by lower uterine segment, cervix,
vagina, vaginal introitus, supported by
ligaments, fascia fat and pelvis floor.
During labour, soft pelvis the passage dilates
to permit foetus to pass from uterus to exterior
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19. Bony Pelvis
 False pelvis above and true pelvis below
 Composed of 4 bones sacrum , coccyx and 2 innominate
bone (fusion of ilium , ischium and pubis)
 Sacrum and coccyx forms the part of vertebral column and the back
wall
 2 innominate bone forms the lateral and anterior wall, joined to the
sacrum at posteriorly sacro iliac joint and to one another at
symphysis pubis anteriorly
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20. Bony Landmarks Of The Pelvis
 The bony landmarks on the brim of the
pelvis from anterior to posterior on
each side are — upper border of
symphysis pubis, pubic crest, pubic
tubercle, pectineal line, iliopubic
eminence, iliopectineal line, sacro-iliac
articulation, anterior border of the ala of
sacrum and sacral promontory
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21. False And True Pelvis
 The false pelvis is formed by the iliac
portions of the innominate bones and is
limited above by the iliac crests.
 It has got little obstetric significance.
 Its only obstetric function is to support the
enlarged uterus during pregnancy. Its
boundaries are: posteriorly — lumbar
vertebrae, laterally — iliac fossa and
anteriorly — anterior abdominal wall.
 The true pelvis is chiefly of concern to the
obstetricians, as it forms the canal through
which the fetus has to pass.
 It is shallow in front, formed by symphysis
pubis and measures 4 cm (1 ½′′) and
deep posteriorly, formed by the sacrum
and coccyx and measures 11.5 cm (4 ½′′).
 For descriptive purpose, it is divided into
inlet, cavity and outlet.
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22. True Pelvis
 True Pelvis Anteriorly – pubis symphysis, posteriorly –
formed by sacrum and coccyx
 Inlet Anteriorly – pubis symphysis, posteriorly – sacral
promontory, laterally – illiopectineal line
 Cavity lies between inlet and outlet is a short curved cannal.
 Outlet anterior - pubic arch, lateral - ischial bones , posterior -
coccyx
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23. Conjugate And
Diagonal
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24. Conjugate
 Obstetric Conjugate- between mid point of
sacral promontory to prominent bony
projection in midline of inner surface of
symphysis pubis (10 cm) measures
indirectly through DC
 Diagonal Conjugate- between lower
border of symphysis pubis to the mid point
of sacral promontory(12 cm) measures,
clinically if not measure pelvis is good and
adequate
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25. Inlet Diameters
 A.P diameter (1) – upper border
of symphysis pubis to sacral
promontory (11 cm)
 Oblique diameter (2)- sacroiliac
joint to the opposite iliopubic
eminence (12 cm)
 Transverse diameter (1)- max
gap between 2 iliac pectineal line
(13 cm)
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26. Cavity And Outlet Diamters
 Cavity AP diameter- mid point of pubis
symphysis to 2nd and 3rd sacral vertebrae
junction (12 cm)
 Outlet AP diameter- lower border of the
symphysis pubis to the tip of coccyx (13
cm)
 Outlet transverse diameter- between
inner border of ischial tuberosity (11cm)
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27. Types Of Female Pelvis
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 Gynaecoid (50%)- inlet shape is round, outlet wide, sub pubic
angle around 85 degree, no difficulty in delivery
 Anthropoid (25%)- anterior posterior longitudinal oval, outlet
slightly narrow, more incidence face to pubis , sub pubic angle
narrow
 Android (20%)- triangular in shape, cavity ischial spine
prominent, outlet narrow, difficulty delivery with increase perennial
injuries, sub pubic angle narrow
 Platypelloid (5%)- transversal oval in shape , outlet very wide
more than 90 degree, no difficulty in delivery just increase time in
mechanism of labour.

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